A year after quitting the tournament mid-round with his game in a shambles, McIlroy cut a contrasting figure on his way to a flawless seven-under-par 63 in relatively benign afternoon conditions at PGA National.
"I made a great par save on nine which kept that bogey-free round alive," the 24-year-old Northern Irishman told Golf Channel after seizing a one-shot lead over American Russell Henley.
Buoyed by that 10-foot par putt at the ninth, McIlroy birdied the next three holes and added further birdies on his last two holes, much to the delight of his parents Gerry and Rosie, who were in the gallery.
"It's a good ball-striker's course," said McIlroy, who looked ominously close to regaining the form that made him the world's top-ranked player at the time of his meltdown 12 months ago.
"If you can keep your ball in play and give yourself plenty of birdie chances, that's the name of the game here."
McIlroy's sizzling start against the strongest field in the world so far this year overshadowed Australian Adam Scott, one of his playing partners on the day.
Not that Scott, gearing up to defend his Masters title in April, started badly as he opened with a 68 to sit five strokes off the pace.
However the Australian's move up the leaderboard stalled when he drowned his tee shot at the par-three 15th, the first of three dangerous holes in a stretch known as the "Bear Trap", in honour of course designer Jack Nicklaus.
Five-times Major champion Phil Mickelson did not do a lot wrong while carding a 70 in the afternoon while world number one Tiger Woods had an inconsistent 71 in the morning and ended the day tied for 81st in a field of 144.
Second-placed Henley started with four consecutive birdies and was five under through six holes but it was a par on his 12th hole, the par-five third, that most impressed.
He pulled his second shot, an "horrendous" six-iron that ended partly submerged in a water hazard, with a bunker between his ball and the hole.
Henley then removed his right shoe and sock and conjured up an outstanding third shot to inside 10 feet, only to miss the birdie putt.
"I've never had that shot in my life," he said. "I tried to treat it like a bunker shot."
Mickelson, meanwhile, was not at his best in his first competitive round as a professional on the course, but he sounded mildly satisfied.
"I did some things really well and some things poorly," the American left-hander said, citing a need to improve his distance control with his irons.
"I've just got to get that fine-tuning down. It's a very difficult course but when you hit good shots you get rewarded with good birdie opportunities."
Fifty-six players broke par on a day when players were allowed preferred lies due to heavy pre-tournament rain that left the fairways damp.
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